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Photochromatic lenses and tints www.eyenirvaan.com

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Photochromatic lenses and tints www.eyenirvaan.com

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Photochromatic lenses and tints www.eyenirvaan.com

  1. 1. PHOTOCHROMATIC LENSES AND TINTS Gopi Vankudre M. Optom, FIACLE To view more presentations and articles, visit www.eyenirvaan.com
  2. 2. PHOTOCHROMATIC LENSES AND TINTS
  3. 3. The Photochromatics  Invented 1964 by Corning  Available as – Glass Photocromatics – Plastic Photocromatics To view more presentations and articles, visit www.eyenirvaan.com
  4. 4. Glass Photochromatics Consist of silver halides Activated by UV radiations between 300- 400nm Do not wear out with repeated darkening and lightening But the lenses do not lighten indoors To view more presentations and articles, visit www.eyenirvaan.com
  5. 5. Plastic Photochromatics Uses Organic crystals instead of In- organic crystals Consist of Indolino spiroresines(ISN) To view more presentations and articles, visit www.eyenirvaan.com
  6. 6. Different manufacturing methods  Imbibition  In-mass  Multimatrix  Dip Coating  Front surface coating  Transbonding To view more presentations and articles, visit www.eyenirvaan.com
  7. 7. Imbibition  Used by Transitions  Starts with clear plastic lens  The surface is infused with photochromatic material To view more presentations and articles, visit www.eyenirvaan.com
  8. 8. In-Mass  Phtochroamtic dye is mixed in the liquid monomer  This is similar to glass photochromatics  In glass – The material reacts throughout the lens – Gives Bulls’s Eye effect To view more presentations and articles, visit www.eyenirvaan.com
  9. 9. In-Mass  In Plastic: – Does not produce the Bulls Eye effect – When the dye near the surface wear out , the dye within matrix absorbs UV – E.g: Corning Sunsensors, Rodenstock ColorMatic To view more presentations and articles, visit www.eyenirvaan.com
  10. 10. Dip coating, Front Surface coating, Transbonding  Not very commonly used  Transbonding: Used for Polycarbonate and High-Index material To view more presentations and articles, visit www.eyenirvaan.com
  11. 11. Multimatrix  Used by Kodak Insta-shades  Begins with clear lens  Has 1 mm photochromatic dye bonded to it To view more presentations and articles, visit www.eyenirvaan.com
  12. 12. Advantages and disadvantages of Photochromics  Glass- 100% UV B and 98% UV A absrption  Plastic Photochromics wear out – depends on number of UV exposures  Glass photochromic fail to fully lighten  They do not replace the sunglasses- For e.g. for person driving a car To view more presentations and articles, visit www.eyenirvaan.com
  13. 13. Factors Influencing Photochromatic Performance  Both glass and plastic – Light Intensity – Temperature  Glass – Previous exposures – Lens thickness  A PG extra lens has 22% transmission for 2mm thickness and 11% for 4mm – Toughening Process To view more presentations and articles, visit www.eyenirvaan.com
  14. 14. Toughening and Photo chromatic effect  Photo chromic lenses should be chemically toughened  Heat hardened lens lightened slower  Also reduces the transmission in the darken stage. To view more presentations and articles, visit www.eyenirvaan.com
  15. 15. When Replacing One Glass Lens  Ideally replace both the lenses  If new lens is hardened , also harden the old lens  Boil the old lens in water for 2 hours  Keep the lens in oven at a temperature of 212˚F  A heat lamp may also be used To view more presentations and articles, visit www.eyenirvaan.com
  16. 16. TINTS IN LENSES
  17. 17. Color Coatings  Metallic oxides are used for absorptive coating  Advantage – May be removed and recoated – Transmission curve are more even – Absorbs the longer wavelength in the near IR region To view more presentations and articles, visit www.eyenirvaan.com
  18. 18. Glass color coatings  Glass color coatings – Coating is uniform regardless the prescription  Color coatings for Plastic Lenses – Plastic lenses are normally dyed and not coated – However CR-39, plastic and high – index material can be color coated To view more presentations and articles, visit www.eyenirvaan.com
  19. 19. Dying plastic lenses  Versatility of tinting  Longer it is kept in dye darker the tint  Dye is absorbed over the surface equally  Disadvantage of poor IR absoption To view more presentations and articles, visit www.eyenirvaan.com
  20. 20. Gradient lenses  Darker upper portion  Lighter lower portion  Produced in plastics To view more presentations and articles, visit www.eyenirvaan.com
  21. 21. Color characteristics  Clear crown glass and cr-39 – Crown glass absorbs light below 290 nm – Cr39 has UV inhibitor blocks UV below 350 nm  Pink – Has uniform transmission – Do not cause color distortion – Reduces internal reflections To view more presentations and articles, visit www.eyenirvaan.com
  22. 22. Color characteristics  Yellow – Absorb shorter visible light – Should not be adviced at night – Increases contrast – Common brand names are Hazemaster (AO) and Kalichrome (B & L) To view more presentations and articles, visit www.eyenirvaan.com
  23. 23. Color characteristics  Brown – Same characteristic of absorbing short wavelength as of yellow tint – Used to improve contrast in bright , hazy and smoggy days To view more presentations and articles, visit www.eyenirvaan.com
  24. 24. Color characteristics  Green – Has similar color sensitivity curve as for the humen eye – Contains ferrous(iron) oxides – Good absorption in UV and IR region To view more presentations and articles, visit www.eyenirvaan.com
  25. 25. Color characteristics  Grey – Most popular for sun protection – Evenness of transmission – Does not cause misjudgment in color vision deficient’s To view more presentations and articles, visit www.eyenirvaan.com
  26. 26. THANK YOU To view more presentations and articles, visit www.eyenirvaan.com

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